The invention relates to an arrangement for the adjustment of the vertical tracking force on a phonograph stylus, such arrangement forming a part of the tone arm upon which the stylus holder is mounted.
Tone arms which are at present phonographs of the hi-fi class are practically only tubular in shape, and are provided with arrangements for the adjustment of the vertical tracking force on the stylus. This arrangement is usually fastened to the rear part of the tone arm behind a supporting bearing dividing the tone arm into a front part with a stylus holder and a rear part with a counterweight, the main task of which is to counterbalance the weight of the front part of the tone arm with the stylus holder, and to achieve a virtual equilibrium. The required vertical tracking force on the stylus is applied so that the whole counterweight or its part is shifted by a turning motion along a thread from the position of equilibrium to the supporting bearing of the tone arm until the front part of the tone arm, due to its larger weight, generates the required vertical force on the stylus according to a scale and an indicator on the counterweight. This method is, in principle, rather simple; the practical solution is, however, complicated, because of the close spacing between the center of gravity of the tone arm and the counterweight. This makes it difficult to provide for an easy adjustment of the vertical tracking force, such arrangement at the same time being resistant to undesirable disturbances during the adjustment of this force. It is also rather difficult to provide a thus arranged counterweight with an effective anti-resonator, or to build it into the tone arm in a fairly simple manner.
In a smaller number of tone arms the counterweight at the rear of the tone arm is assigned the sole task of balancing the tone arm in order to obtain an equilibrium, whereby the vertical tracking force on the stylus is adjusted either by a small weight on the front part of the tone arm or by a spring for a vertical movement arranged near the supporting bearing. This small weight on the front part of the tone arm, however, increases the effective weight of the arm, while the use of a spring is generally more complicated and usually less accurate.